In recent years, for the purpose of energy conservation and prevention of further global warming, research and development of lighting devices employing light emitting diodes (LEDs) have been conducted in the field of lighting. LEDs can achieve higher energy efficiency than conventional incandescent light bulbs and the like.
For example, a conventional incandescent light bulb offers an energy efficiency of tens of [lm/W]. In contrast, LEDs, when used as a light source, achieve higher energy efficiency—more specifically, an energy efficiency of 100 [lm/W] or higher (hereinafter, a lamp equipped with the LEDs and designed to replace another light bulb is referred to as an “LED light bulb”).
Patent Literature 1 and the like introduce an LED light bulb that can replace a conventional incandescent light bulb. The LED light bulb disclosed in Patent Literature 1 is structured as follows. A substrate, on which a plurality of LEDs have been mounted, is mounted on and secured to an edge surface of an outer shell, inside which a lighting circuit for lighting the LEDs (causing the LEDs to emit light) is disposed. The LEDs are covered by a dome-shaped globe. The LED light bulb is lit when the lighting circuit causes the LEDs to emit light.
This LED light bulb has a similar external shape to a conventional incandescent light bulb and comprises an Edison screw as a power supply terminal. Therefore, this LED light bulb can be attached to a socket of a lighting device to which a conventional incandescent light bulb is customarily attached.